Skin is subject to abuse by many extrinsic (environmental) factors as well as intrinsic (chronoaging) factors. A common extrinsic factor is exposure to ultraviolet radiation. Whether extrinsic or intrinsic, the abuse results in wrinkling of the skin. To many people, skin wrinkles are a reminder of the disappearance of youth. As a result, the elimination of wrinkles has become a booming business in youth-conscious societies. Treatments range from cosmetic creams and moisturizers to various forms of cosmetic surgery.
Chronoaging results in the thinning and general degradation of skin. As the skin naturally ages, there is a reduction in the cells and blood vessels that supply the skin. There is also a flattening of the dermal-epidermal junction which results in weaker mechanical resistance of this junction. As a consequence, older persons are more susceptive to blister formation in cases of mechanical trauma or disease processes. (See Oikarinen, (1990) "The Aging of Skin: Chronoaging Versus Photoaging", Photodermatal. Photoimmunol. Photomed., Vol. 7, pp 3-4).
It is known to use salicyclic acid for the treatment of acne, see for example, U.S Pat. Nos. 4,891,227 and 4,891,228, to Thaman et al., both issued Jan. 2, 1990 the disclosures of which are incorporated herein. Further, salicylic acid has been used for the removal of wart, corns and calluses; for the treatment of psoriasis, seborrheic dermatitis and dandruff; and for the topical treatment of ringworm infection. A listing of commercially available products containing salicylic acid will be found in the Physician's Desk Reference, 45th Edition, 1991, page 323. However, these prior art uses of salicylic acid have generally involved short term treatments in which relatively large doses of the acid are applied (i.e., sufficient to cause significant irritation and often peeling) in order to obtain a cure or treatment of the particular condition, such as removal of comedones, as opposed to persistent treatment of normal aging skin.